Heretofore, in various industrial fields, gelling agents have been used to solidify a liquid substance, that is, jellify or thicken it. For example, they have been used to control the fluidity of an adhesive, coating composition, printing ink or cosmetic, to provide thixotropy, to collect oil outflowing into the sea and to dispose of cooking oil for domestic use and for other purposes in the food manufacturing industry and the medical field. Out of these, gelling agents which solidify water include collagen, gelatin, Japan agar, agar (carrageenan) andpectin, and there are other gelling agents for solidifying organic substances, especially hydrocarbons, alcohols, ketones, esters, other organic solvents and solutions containing any one of them as the main ingredient.
Out of these, gelling agents for solidifying an organic solution include low-molecular weight or high-molecular weight organic compounds. As gelling agents which are low-molecular weight organic compounds, there are known low-molecular weight organic compounds having a hydrogen bonding functional group such as amino group, imide group or urea group in the molecule. As gelling agents which are high-molecular weight organic compounds, there are known polyvinyl alcohol/polyethylene/elastomers, urea resin and polyolefin unwoven fabrics which introduce an oil in the molecule entangled with a high-molecular weight polymer having lipophilic nature to swell it but keep their solid state.
Conventional gelling agents for solidifying an organic solution must be generally used in large quantities, for example, about 5 to 10% based on the solution or tends to change into sol to return to a liquid state at a relatively low temperature, for example, 30 to 40° C. Therefore, it has been desired to improve these disadvantages.
Use of a large amount of a gelling agent for gelatinization is not only economically disadvantageous but also increases the amount of foreign matter contained in a solvent to be gelatinized. When the gelatinized solvent is used, the influence of the gelling agent as an impurity cannot be ignored.
When the upper limit of the gelation temperature is low, the gelling agent may not keep its shape or fluidize to cause a leak due to a small increase in temperature.
Then, the development of a gelling agent which can keep a gel state with a small amount and at a relatively high temperature has been desired.
The inventors of the present invention aimed to develop a gelling agent capable of keeping a gel state even at a relatively high temperature even when it is used in a small amount and already proposed ethers, thioethers and sulfones having a specific structure with a perfluoroalkyl group and a hydrocarbon group (refer to JP-A 2007-191661, JP-A 2007-191627, JP-A 2007-191626 and the pamphlet of International Laid-open 2009/078268).
These low-molecular weight organic gelling agents can keep an organic solution in a gel state even when it is used in a relatively small amount or at a relatively high temperature.